Electronic device with proximity-based radio power control

ABSTRACT

An electronic device such as a portable electronic device may have an antenna and associated wireless communications circuitry. A sensor such as a proximity sensor may be used to detect when the electronic device is in close proximity to a user&#39;s head. Control circuitry within the electronic device may be used to adjust radio-frequency signal transmit power levels. When it is determined that the electronic device is within a given distance from the user&#39;s head, the radio-frequency signal transmit power level may be reduced. When it is determined that the electronic device is not within the given distance from the user&#39;s head, proximity-based limits on the radio-frequency signal transmit power level may be removed. Data may be gathered from a touch sensor, accelerometer, ambient light sensor and other sources for use in determining how to adjust the transmit power level.

This application claims the benefit of provisional patent applicationNo. 61/059,247, filed Jun. 5, 2008, and U.S. patent application Ser. No.12/207,326 filed Sep. 9, 2008, which are hereby incorporated byreference herein in their entirety.

BACKGROUND

This invention relates generally to electronic devices, and moreparticularly, to power control techniques for radio-frequency circuitryin electronic devices.

Electronic devices such as handheld electronic devices and otherportable electronic devices are becoming increasingly popular. Examplesof handheld devices include handheld computers, cellular telephones,media players, and hybrid devices that include the functionality ofmultiple devices of this type. Popular portable electronic devices thatare somewhat larger than traditional handheld electronic devices includelaptop computers and tablet computers.

Due in part to their mobile nature, portable electronic devices areoften provided with wireless communications capabilities. For example,handheld electronic devices may use long-range wireless communicationsto communicate with wireless base stations. Cellular telephones andother devices with cellular capabilities may communicate using cellulartelephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz. Portableelectronic devices may also use short-range wireless communicationslinks. For example, portable electronic devices may communicate usingthe Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz and the Bluetooth®band at 2.4 GHz. Data communications are also possible at 2100 MHz.

To satisfy consumer demand for small form factor wireless devices,manufacturers are continually striving to reduce the size of componentsthat are used in these devices while providing enhanced functionality.It is generally impractical to completely shield a user of a compacthandheld device from transmitted radio-frequency signals. For example,conventional cellular telephone handsets generally emit signals in thevicinity of a user's head during telephone calls. Government regulationslimit radio-frequency signal powers. In particular, so-called specificabsorption rate (SAR) standards are in place that impose maximum energyabsorption limits on handset manufacturers. At the same time, wirelesscarriers require that the handsets that are used in their networks becapable of producing certain minimum radio-frequency powers so as toensure satisfactory operation of the handsets.

The manufacturers of electronic devices such as wireless handhelddevices therefore face challenges in producing devices with adequateradio-frequency signal strengths that are compliant with applicablegovernment regulations.

It would therefore be desirable to be able to provide electronic deviceswith improved wireless capabilities.

SUMMARY

An electronic device such as a handheld electronic device or otherportable electronic device may be provided that has wirelesscommunications capabilities. An antenna may be used to transmit andreceive radio-frequency signals. The signals may be associated withcellular telephone communications bands.

A proximity sensor may be provided in the device. The proximity sensormay include a light source such as a light-emitting diode and aphotodetector. During operation of the device, the light source emitslight. If an object such as the head of a user is within a givendistance of the electronic device, the emitted light will be reflectedback to the electronic device and will be detected by the photodetector.This allows the electronic device to determine whether the electronicdevice is in close proximity to the user's head.

Information on whether the electronic device is close to the user's headmay also be gathered using data from other sources. For example, theelectronic device may have a touch screen with a touch sensor or mayhave other touch sensitive components. Signals from these touch sensorsmay be used to help determine whether the electronic device is adjacentto the user's head. The electronic device may also have sensors such asan ambient light sensor and an accelerometer. The ambient light sensormay detect when a shadow passes over the front face of the device, whichmay be indicative of a close distance between the electronic device andan external object. The accelerometer may produce data that isindicative of the current orientation of the electronic device relativeto the ground and data that is indicative of whether the device is inmotion or at rest. In situations in which the device is being held in anorientation in which one of the edges of the device faces the ground andin which the device is in motion, the electronic device can concludethat the electronic device is in close proximity to the user's head.

The electronic device may have an adjustable radio-frequency poweramplifier. The device may adjust the output power from theradio-frequency power amplifier to control the power level oftransmitted cellular telephone signals. If it is determined that theelectronic device is close to the user's head, the maximum allowabletransmit power level may be limited. If it is determined that theelectronic device is not in close proximity to the user's head, theradio-frequency transmit power of the device need not be limited.

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and the followingdetailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative portable electronicdevice in accordance with an embodiment of the present invention.

FIG. 2 is a schematic diagram of an illustrative portable electronicdevice in accordance with an embodiment of the present invention.

FIG. 3 is a diagram of an illustrative electronic device showing howsensors may be used to detect when the electronic device is in thevicinity of an object such as a human body part in accordance with anembodiment of the present invention.

FIG. 4 is a diagram of illustrative circuitry that may be used in anelectronic device such as a wireless portable electronic device withoutput power control capabilities in accordance with an embodiment ofthe present invention.

FIG. 5 is a flow chart of illustrative steps involved in controllingtransmitted radio-frequency power in a wireless electronic device inaccordance with an embodiment of the present invention.

FIG. 6 is a graph showing how transmitted radio-frequency signal powercan be controlled as a function of time in response to network controlcommands and locally established power limits based on data such asproximity sensor data in accordance with an embodiment of the presentinvention.

FIG. 7 is a flow chart of illustrative steps involved in gathering andanalyzing data in a wireless electronic device to determine appropriateradio-frequency signal power settings for transmitted signals inaccordance with an embodiment of the present invention.

FIG. 8 is a flow chart of illustrative steps involved in gathering andanalyzing data in a wireless electronic device to determine appropriateradio-frequency signal power settings for transmitted signals inscenarios in which one or more communications bands are being used inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention relates generally to electronic devices, and moreparticularly, to managing transmitted radio-frequency power levels inportable electronic devices such as handheld electronic devices.

The electronic devices may be portable electronic devices such as laptopcomputers or small portable computers of the type that are sometimesreferred to as ultraportables. Portable electronic devices may also besomewhat smaller devices. Examples of smaller portable electronicdevices include wrist-watch devices, pendant devices, headphone andearpiece devices, and other wearable and miniature devices. With onesuitable arrangement, the portable electronic devices may be wirelesselectronic devices.

The wireless electronic devices may be, for example, handheld wirelessdevices such as cellular telephones, media players with wirelesscommunications capabilities, handheld computers (also sometimes calledpersonal digital assistants), remote controllers, global positioningsystem (GPS) devices, and handheld gaming devices. The wirelesselectronic devices may also be hybrid devices that combine thefunctionality of multiple conventional devices. Examples of hybridportable electronic devices include a cellular telephone that includesmedia player functionality, a gaming device that includes a wirelesscommunications capability, a cellular telephone that includes game andemail functions, and a portable device that receives email, supportsmobile telephone calls, has music player functionality and supports webbrowsing. These are merely illustrative examples.

An illustrative portable electronic device in accordance with anembodiment of the present invention is shown in FIG. 1. Device 10 ofFIG. 1 may be, for example, a handheld electronic device that supports2G and/or 3G cellular telephone and data functions, global positioningsystem capabilities, and local wireless communications capabilities(e.g., IEEE 802.11 and Bluetooth®) and that supports handheld computingdevice functions such as internet browsing, email and calendarfunctions, games, music player functionality, etc.

Device 10 may have housing 12. Antennas for handling wirelesscommunications may be housed within housing 12 (as an example).

Housing 12, which is sometimes referred to as a case, may be formed ofany suitable materials including, plastic, glass, ceramics, metal, orother suitable materials, or a combination of these materials. In somesituations, housing 12 or portions of housing 12 may be formed from adielectric or other low-conductivity material, so that the operation ofconductive antenna elements that are located in proximity to housing 12is not disrupted. Housing 12 or portions of housing 12 may also beformed from conductive materials such as metal. An advantage of forminghousing 12 from a dielectric material such as plastic is that this mayhelp to reduce the overall weight of device 10.

In scenarios in which housing 12 is formed from metal elements, one ormore of the metal elements may be used as part of the antennas in device10. For example, metal portions of housing 12 may be shorted to aninternal ground plane in device 10 to create a larger ground planeelement for that device 10. Housing 12 may have a bezel such as bezel 14that surrounds display 16. Bezel 14 may be formed from a conductivematerial or other suitable material and may be used as part of theantennas in device 10. For example, bezel 14 may be shorted to printedcircuit board conductors or other internal ground plane structures indevice 10 to form part of an antenna ground plane.

Display 16 may be a liquid crystal display (LCD), an organiclight-emitting diode (OLED) display, or any other suitable display. Theoutermost surface of display 16 may be formed from one or more plasticor glass layers. If desired, touch screen functionality may beintegrated into display 16 or may be provided using a separate touch paddevice. An advantage of integrating a touch screen into display 16 tomake display 16 touch sensitive is that this type of arrangement cansave space and reduce visual clutter. Touch screen displays such asdisplay 16 may be formed from capacitive touch sensors or any othersuitable touch sensors (e.g., resistive touch sensors, touch sensorsbased on light or sound waves, etc.). An advantage of capacitive touchsensors is that they may be used to sense the presence of an object evenwhen the object is not in direct contact with display 16.

Display screen 16 (e.g., a touch screen) is merely one example of aninput-output device that may be used with electronic device 10. Ifdesired, electronic device 10 may have other input-output devices. Forexample, electronic device 10 may have user input control devices suchas button 19, and input-output components such as port 20 and one ormore input-output jacks (e.g., for audio and/or video). Button 19 maybe, for example, a menu button. Port 20 may contain a 30-pin dataconnector (as an example). Openings 22 and 24 may, if desired, formspeaker and microphone ports. Speaker port 22 may be used when operatingdevice 10 in speakerphone mode. Opening 23 may also form a speaker port.For example, speaker port 23 may serve as a telephone receiver that isplaced adjacent to a user's ear during operation. In the example of FIG.1, display screen 16 is shown as being mounted on the front face ofhandheld electronic device 10, but display screen 16 may, if desired, bemounted on the rear face of handheld electronic device 10, on a side ofdevice 10, on a flip-up portion of device 10 that is attached to a mainbody portion of device 10 by a hinge (for example), or using any othersuitable mounting arrangement.

A user of electronic device 10 may supply input commands using userinput interface devices such as button 19 and touch screen 16. Suitableuser input interface devices for electronic device 10 include buttons(e.g., alphanumeric keys, power on-off, power-on, power-off, and otherspecialized buttons, etc.), a touch pad, pointing stick, or other cursorcontrol device, a microphone for supplying voice commands, or any othersuitable interface for controlling device 10. Although shownschematically as being formed on the top face of electronic device 10 inthe example of FIG. 1, buttons such as button 19 and other user inputinterface devices may generally be formed on any suitable portion ofelectronic device 10. For example, a button such as button 19 or otheruser interface control may be formed on the side of electronic device10. Buttons and other user interface controls can also be located on thetop face, rear face, or other portion of device 10. If desired, device10 can be controlled remotely (e.g., using an infrared remote control, aradio-frequency remote control such as a Bluetooth® remote control,etc.).

Device 10 may contain sensors that provide information about theenvironment and condition of device 10. For example, device 10 maycontain a proximity sensor such as sensor 25 and an ambient light sensorsuch as ambient light sensor 27.

Proximity sensor 25 may include, for example, a light-emitting diode(LED) and an associated photodetector such as a photodiode. Thelight-emitting diode may be an infrared light-emitting diode (as anexample). Reflected light from nearby objects may be detected using thephotodiode. When sufficient reflected light is detected, it can beconcluded that a human body part (e.g., a head, finger, or hand) orother object is located close to sensor 25. When insufficient reflectedlight is detected, it can be concluded that no objects are located nearto sensor 25. If desired, emitted light from sensor 25 may beconcentrated at a particular distance from sensor 25 using a lens orother focusing structure. This may help to enhance the strength ofreflected signals from objects located at this particular distance(e.g., objects located at 0.5 to 10 cm away from the planar frontsurface of display 16).

The light-emitting diode in the proximity sensor may be modulated at aparticular frequency or may be modulated using any other suitablemodulation pattern. The use of a modulation pattern to drive thelight-emitting diode may help to discriminate reflected light-emittingdiode signals from background illumination. This may increase thesignal-to-noise ratio of the proximity sensor. If desired, proximitysensor 25 may be based on proximity detection arrangements other thanlight-emitting diode arrangements. For example, a proximity sensor fordevice 10 may be based on a capacitive sensor, a photodetector thatworks only with ambient light (and not emitted light from device 10), anacoustic proximity sensor (e.g., a sensor that uses ultrasonic soundwaves to determine the presence or absence of a nearby object), a sensorthat detects reflected electromagnetic radiation (e.g., radio-frequencyradiation), or any other suitable sensor capable of detecting thepresence of a nearby object.

Ambient light sensor 27 may be used to detect the level of ambientillumination around device 10. Ambient light sensor 27 may beimplemented using a photodiode that is sensitive to visible light.Separate photodiodes are typically used for proximity sensor 25 andambient light sensor 27, but the photodiode functionality of ambientlight sensor 27 and the photodiode functionality of proximity sensor 25(in a light-based proximity detector) may be implemented using a commonphotodiode if desired. Information on the amount of light that isgathered by ambient light sensor 27 may be used to adjust the screenbrightness of display 16 (as an example).

If desired, proximity sensor functionality may be implemented in device10 using a device that serves multiple functions. As an example, acapacitive touch sensor or other such touch sensor that is part of atouch display 16 may be used in detecting the presence of a nearbyobject. During normal operation, touch sensor output signals may be usedto identify user input selections as a user presses a finger againstvarious portions of screen 16. When used as a proximity sensor, theoutput signals of the touch screen may be processed to determine whetheror not an object is adjacent to device 10. With this type ofarrangement, the capacitive readings obtained from the touch sensorportion of display 16 may be processed, for example, to determinewhether a user has placed device 10 next to the user's head. Because thepresence of the user's head in the vicinity of screen 16 will change thecapacitive reading (or other such touch sensor reading) from thedisplay, the presence of the user's head can be detected without using aconventional proximity sensor. As another example, light readings froman ambient light sensor may be used as an indicator of the proximity ofan object to device 10 (e.g., by detecting shadows that indicate thepresence of an object). Touch pads without displays may also be used toproduce proximity data.

To improve accuracy, signals from multiple proximity sensor devices(e.g., an LED-based proximity sensor, an ambient light sensor used todetect proximity, a capacitive touch screen, etc.) may be processed inparallel. With this type of arrangement, device 10 can more accuratelydetermine whether or not device 10 has been placed in close proximity toan object.

The locations for proximity sensor 25 and ambient light sensor 27 ofFIG. 1 are merely illustrative. Sensors such as these may be placed atany suitable location on device 10. When a location such as the locationshown in FIG. 1 is used, sensors 25 and 27 obtain information on whetherthe upper end of device 10 has been placed adjacent to a user's ear andhead. This type of configuration arises when a user is using device 10for a cellular telephone call. When using device 10 to make a telephonecall, receiver 23 is placed immediately adjacent to the user's ear,whereas microphone port 24 is placed close to the user's mouth. Ifdesired, sensors such as proximity sensor 25 and/or ambient light sensor25 may be located at the lower (microphone) end of device 10. Forexample, proximity sensor 25 may be placed adjacent to menu button 19 tohelp sense when microphone 24 is adjacent to the user's face.

Components such as display 16 and other user input interface devices maycover most of the available surface area on the front face of device 10(as shown in the example of FIG. 1) or may occupy only a small portionof the front face of device 10. Because electronic components such asdisplay 16 often contain large amounts of metal (e.g., asradio-frequency shielding), the location of these components relative tothe antenna elements in device 10 should generally be taken intoconsideration. Suitably chosen locations for the antenna elements andelectronic components of the device will allow the antennas ofelectronic device 10 to function properly without being disrupted by theelectronic components.

Examples of locations in which antenna structures may be located indevice 10 include region 18 and region 21. These are merely illustrativeexamples. Any suitable portion of device 10 may be used to house antennastructures for device 10 if desired.

Any suitable antenna structures may be used in device 10. For example,device 10 may have one antenna or may have multiple antennas. Theantennas in device 10 may each be used to cover a single communicationsband or each antenna may cover multiple communications bands. Ifdesired, one or more antennas may cover a single band while one or moreadditional antennas are each used to cover multiple bands.

In arrangements in which antennas are needed to support communicationsat more than one band, the antennas may have shapes that supportmulti-band operations. For example, an antenna may have a resonatingelement with arms of various different lengths and/or a ground planewith slots of various different sizes that resonate in desiredradio-frequency bands. Inverted-F antenna elements, planar inverted-Fantenna elements or other antenna structures may be used in the presenceof an antenna slot to form a hybrid slot/non-slot antenna.

Antennas (e.g., hybrid slot/non-slot antennas or other suitableantennas) may be used at one end or both ends of device 10. For example,one such antenna may be used as a dual band antenna (e.g., in region 21)and one such antenna may be used as a pentaband antenna (e.g., in region18).

When an antenna in region 18 is used as a cellular telephone antenna(e.g., for 2G and/or 3G voice and data communications), the antenna willbe located at the same end of device 10 as microphone port 24. Whendevice 10 is being held close to the user's head and microphone 24 isbeing used to conduct a telephone call, the antenna in region 18 will benear to the user's head and will therefore be likely to emitradio-frequency signals near the user's head. Proximity detector 25 andother sensors may be used in detecting the presence of the user's heador other nearby object. To ensure that regulatory limits onradio-frequency emissions in the vicinity of the user's head aresatisfied, device 10 may reduce the maximum allowable transmittedradio-frequency signal power that is handled by the antenna in region 18whenever it is determined that device 10 is in the vicinity of theuser's head (i.e., whenever proximity detector 25 and/or other sensorsdetermine that an object is within a few centimeters or other suitabledistance from the front face of device 10).

A schematic diagram of an embodiment of an illustrative portableelectronic device such as a handheld electronic device is shown in FIG.2. Portable device 10 may be a mobile telephone, a mobile telephone withmedia player capabilities, a handheld computer, a remote control, a gameplayer, a global positioning system (GPS) device, a laptop computer, atablet computer, an ultraportable computer, a hybrid device thatincludes the functionality of some or all of these devices, or any othersuitable portable electronic device.

As shown in FIG. 2, device 10 may include storage 34. Storage 34 mayinclude one or more different types of storage such as hard disk drivestorage, nonvolatile memory (e.g., flash memory or otherelectrically-programmable-read-only memory), volatile memory (e.g.,battery-based static or dynamic random-access-memory), etc.

Processing circuitry 36 may be used to control the operation of device10. Processing circuitry 36 may be based on a processor such as amicroprocessor and other suitable integrated circuits. With one suitablearrangement, processing circuitry 36 and storage 34 are used to runsoftware on device 10, such as internet browsing applications,voice-over-internet-protocol (VOIP) telephone call applications, emailapplications, media playback applications, operating system functions,etc. Processing circuitry 36 and storage 34 may be used in implementingsuitable communications protocols. Communications protocols that may beimplemented using processing circuitry 36 and storage 34 includeinternet protocols, wireless local area network protocols (e.g., IEEE802.11 protocols—sometimes referred to as Wi-Fi®), protocols for othershort-range wireless communications links such as the Bluetooth®protocol, protocols for handling 3 G communications services (e.g.,using wide band code division multiple access techniques), 2G cellulartelephone communications protocols, etc.

Input-output devices 38 may be used to allow data to be supplied todevice 10 and to allow data to be provided from device 10 to externaldevices. Display screen 16, button 19, microphone port 24, speaker port22, and dock connector port 20 are examples of input-output devices 38.

Input-output devices 38 may include sensors 41. Sensors 41 may includeproximity sensors such as proximity sensor 25 of FIG. 1, ambient lightsensors such as ambient light sensor 27, accelerometers (e.g., todetermine the orientation of device 10 in real time), sensors formed byutilizing the capabilities of devices such as touch screen 16 or othermultipurpose components in device 10, acoustic sensors, electromagneticsensors, or any other suitable sensors.

Input-output devices 38 can also include user input-output devices 40such as buttons, touch screens, joysticks, click wheels, scrollingwheels, touch pads, key pads, keyboards, microphones, cameras, etc. Auser can control the operation of device 10 by supplying commandsthrough user input devices 40. Display and audio devices 42 may includeliquid-crystal display (LCD) screens or other screens, light-emittingdiodes (LEDs), and other components that present visual information andstatus data. Display and audio devices 42 may also include audioequipment such as speakers and other devices for creating sound. Displayand audio devices 42 may contain audio-video interface equipment such asjacks and other connectors for external headphones and monitors.

Wireless communications devices 44 may include communications circuitrysuch as radio-frequency (RF) transceiver circuitry formed from one ormore integrated circuits, power amplifier circuitry, passive RFcomponents, antennas, and other circuitry for handling RF wirelesssignals. Wireless signals can also be sent using light (e.g., usinginfrared communications).

Device 10 can communicate with external devices such as accessories 46,computing equipment 48, and wireless network 49 as shown by paths 50 and51. Paths 50 may include wired and wireless paths. Path 51 may be awireless path. Accessories 46 may include headphones (e.g., a wirelesscellular headset or audio headphones) and audio-video equipment (e.g.,wireless speakers, a game controller, or other equipment that receivesand plays audio and video content), a peripheral such as a wirelessprinter or camera, etc.

Computing equipment 48 may be any suitable computer. With one suitablearrangement, computing equipment 48 is a computer that has an associatedwireless access point (router) or an internal or external wireless cardthat establishes a wireless connection with device 10. The computer maybe a server (e.g., an internet server), a local area network computerwith or without internet access, a user's own personal computer, a peerdevice (e.g., another portable electronic device 10), or any othersuitable computing equipment.

Wireless network 49 may include any suitable network equipment, such ascellular telephone base stations, cellular towers, wireless datanetworks, computers associated with wireless networks, etc. For example,wireless network 49 may include network management equipment thatmonitors the wireless signal strength of the wireless handsets (cellulartelephones, handheld computing devices, etc.) that are in communicationwith network 49.

To improve the overall performance of the network and to ensure thatinterference between handsets is minimized, the network managementequipment may send power adjustment commands (sometimes referred to astransmit power control commands) to each handset. The transmit powercontrol settings that are provided to the handsets direct handsets withweak signals to increase their transmit powers, so that their signalswill be properly received by the network. At the same time, the transmitpower control settings may instruct handsets whose signals are beingreceived clearly at high power to reduce their transmit power controlsettings. This reduces interference between handsets and allows thenetwork to maximize its use of available wireless bandwidth.

When devices such as device 10 receive transmit power control settingsfrom the network, each device 10 may make suitable transmission poweradjustments. For example, a device 10 may adjust the gain of theradio-frequency power amplifier circuitry that is used to amplify theradio-frequency signals that are being transmitted by device 10 to ahigher level to increase the power of the transmitted radio-frequencysignals or to a lower level to decrease the power of the transmittedradio-frequency signals.

The antenna structures and wireless communications devices of device 10may support communications over any suitable wireless communicationsbands. For example, wireless communications devices 44 may be used tocover communications frequency bands such as cellular telephone voiceand data bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz (asexamples). Devices 44 may also be used to handle the Wi-Fi® (IEEE802.11) bands at 2.4 GHz and 5.0 GHz (also sometimes referred to aswireless local area network or WLAN bands), the Bluetooth® band at 2.4GHz, and the global positioning system (GPS) band at 1575 MHz.

Device 10 can cover these communications bands and/or other suitablecommunications bands using the antenna structures in wirelesscommunications circuitry 44. As an example, a pentaband cellulartelephone antenna may be provided at one end of device 10 (e.g., inregion 18) to handle 2G and 3G voice and data signals and a dual bandantenna may be provided at another end of device 10 (e.g., in region 21)to handle GPS and 2.4 GHz signals. The pentaband antenna may be used tocover wireless bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100MHz (as an example). The dual band antenna may be used to handle 1575MHz signals for GPS operations and 2.4 GHz signals (for Bluetooth® andIEEE 802.11 operations). These are merely illustrative arrangements. Anysuitable antenna structures may be used in device 10 if desired.

Regulatory compliance can be ensured by reducing the maximum allowabletransmitted radio-frequency signal power from device 10 when device 10is in the vicinity of a user's head or other body part. As shown in FIG.3, a typical system environment such as environment 80 includes device10 and an object such as object 60. Object 60 may be an inanimate objector, more significantly, may be part of the user's body such as a user'shead. The energy density associated with radio-frequency emissions fromdevice 10 is generally negligible for IEEE 802.11 and Bluetooth®transmissions (e.g., transmissions that may be associated with antenna62). The process of receiving and processing GPS signals also generallyresults in radio-frequency emissions of negligible energy densities.

In contrast, cellular telephone transmissions (e.g., transmissions thatmay be associated with antenna 64) may have nonnegligible energydensities. This is particularly true for 3G wireless transmissions,which use code-division multiple access (CDMA) coding schemes, ratherthan the time-division multiplexing (TDM) schemes associated with 2G GSMcellular telephone transmissions. Compliance with regulations that placeupper limits on the amount of radio-frequency signal power that may beabsorbed by a user's head can be ensured by reducing the power of theradio-frequency signal transmissions associated with antenna (e.g.,cellular telephone transmissions) whenever it is determined that device10 is adjacent to the user's head.

As shown in FIG. 3, device 10 may have control circuitry 72 (e.g.,processing circuitry 36, storage 34, and other circuitry from FIG. 2).Control circuitry 72 may process sensor signals to detect object 60.

Sensors that may be used to detect the presence of object 60 in thevicinity of device 10 may include proximity sensor 25. Proximity sensor25 may include a light-emitting element such as a laser orlight-emitting diode. Proximity sensor 25 may also have alight-detecting element. In the example of FIG. 3, proximity sensor 25has light-emitting diode 25A and a light detecting element such asphotodiode 25B. Sensor 25 may use light in any suitable frequency range.For example, sensor 25 may use infrared light. Light 74 that is emittedby diode 25A may be reflected from object 60. Reflected light 76 may bedetected by detector (sensor) 25B. If desired, diode 25A may be drivenwith a modulated signal so that light 74 is modulated. For example,light 74 may be modulated at a particular frequency. Using a bandpassfilter centered at the modulation frequency or other suitable filteringarrangement, the signals from sensor 25B may be filtered by controlcircuitry 72 to subtract background noise (as an example). Techniquessuch as these may be used to increase the signal-to-noise ratio of themeasurement signals produced by proximity detector 25.

Another sensor that may be used in device 10 when detecting the presenceof object 60 is ambient light sensor 68. Ambient light sensor 68 may bea photodiode or other light sensor that is capable of detecting incominglight 78. Ambient light sensor 68 may, for example, operate in thevisible spectrum and/or in the infrared spectrum. Because more light 78will generally be received by sensor 68 when sensor 68 is not blocked bythe presence of object 60 than when object 60 is present and is castinga shadow on sensor 68, sensor 68 may be used to generate proximity data.This data may be used alone or in conjunction with proximity data fromother sensors in assisting device 10 in determining whether or notobject 60 is present.

Touch screen 16 may be located on the front face of device 10 (i.e., theside of device 10 that is shown as facing object 60 in the example ofFIG. 3). As shown in FIG. 3, Touch sensor 16, may be a capacitive touchsensor having associated capacitances such as capacitance 66. Themagnitude of this capacitance (and inputs from the other sensors in FIG.3) may be monitored by control circuitry 72. When object 60 is presentin the vicinity of touch screen 16, the magnitude of capacitance 66 willbe affected, which allows control circuitry 72 and device 10 to concludethat object 60 is adjacent to device 10 as shown in FIG. 3.

The detection range of proximity detector 25 and the other sensors indevice 10 is typically in the millimeter to centimeter range. Objectscloser than the maximum detection distance will be sensed as being inthe vicinity of device 10. Objects outside of the detection range willnot be considered to be in the vicinity of device 10. If desired, otherdetection ranges may be used (e.g., detection ranges on the order oftens of centimeters). More typically, however, detection of the presenceof object 60 only when object 60 is closer than several centimeters fromdevice 10 is preferred, as this addresses the primary situation in whichthe energy density of radio-frequency emissions from antenna 64 is ofconcern.

If desired, sensors such as accelerometer 70 may be used in conjunctionwith other sensors to help determine when to adjust the power levelassociated with transmitted radio-frequency signals in device 10.Accelerometer 70 may be used by control circuitry 72 to determine theorientation of device 10 relative to the ground. For example,accelerometer 70 may be used to determine whether device 10 is beingheld by a user so that one of its left or right edges is facingdownwards (as when making a telephone call) or whether device 10 isresting horizontally on a table top. If it is determined that device 10is horizontal and stationary, it may be concluded that it is impossibleor at least unlikely that device 10 is being held in the vicinity of theuser's head. This information may be used to help ascertain whether thereadings obtained from the other sensors in device 10 are accurate.

During operation of device 10, control circuitry 72 may be aware of thetypes of radio-frequency signals that are being transmitted. Forexample, control circuitry 72 might determine that low-powerradio-frequency signals are being transmitted over antenna 62 and thatantenna 64 is not being used. Control circuitry 72 might also determinewhen antenna 64 is being used for 2 G communications (and is thereforeassociated with relatively lower emission levels when averaged overtime) and when antenna 64 is being used for 3 G communications (and istherefore associated with relatively larger time-averaged emissionsbecause no time division multiplexing is being used). Control circuitry72 can use operational information such as this in determining how toadjust the transmitted radio-frequency power from antenna 64, while atthe same time making power adjustment decisions based on the readings ofone or more sensors (e.g., to determine whether object 60 is in closeproximity to device 10). As an example, if it is determined that 2Gsignals are being transmitted, control circuitry 72 can decide to makeno transmit power reductions regardless of the readings of proximitysensor 25, whereas control circuitry 72 can make transmit powerreductions when it is determined that 3G signals are being transmitted.

An illustrative control arrangement that may be used in controllingtransmitted radio-frequency signal powers is shown in FIG. 4. As shownin FIG. 4, control circuitry 72 may include one or more integratedcircuits such as a microprocessor (sometimes referred to as anapplication processor), a baseband module, power management chips,memory, codecs, etc. Transceiver circuitry 84 may be used in producingradio-frequency output signals based on data received from theapplication processor. Circuitry such as circuitry 84 may, if desired,be integrated into one or more of the integrated circuits in controlcircuitry 72.

Radio-frequency signals that are to be transmitted by device 10 aregenerally amplified using radio-frequency amplifier circuitry. Theradio-frequency amplifier circuitry may be implemented using one or moregain stages in one or more integrated circuits. In the example of FIG.4, signals are shown as being amplified by radio-frequency poweramplifier 86. If desired, there may be multiple power amplifiers such asamplifier 86 each of which is associated with a different communicationsband or set of communications bands. A single power amplifier symbol isshown in the schematic diagram of FIG. 4 to avoid over-complicating thedrawing.

Power amplifier circuitry 86 may be used to amplify radio-frequencysignals prior to transmission over antenna 64. The gain of poweramplifier circuitry 86 may be adjusted using a control path such ascontrol path 90. Control path 90 may be used to handle analog and/ordigital control signals. The gain of power amplifier 86 may, forexample, be controlled by adjusting the magnitude of an analog controlvoltage or analog power supply voltage. The gain of power amplifier 86may also be adjusted by turning on and off certain gain stages in poweramplifier 86. If desired, digital control signals may be processed bypower amplifier 86 and used in controlling the gain setting.Combinations of these approaches or other suitable power amplifier gainadjustments techniques may be used if desired.

The gain of power amplifier 86 may be adjusted to ensure that thestrength of the radio-frequency signals that are being transmittedthrough antenna 64 is sufficient for satisfactory wirelesscommunications, while not exceeding regulatory limits. Either an openloop or closed loop control scheme may be used when controlling theoperation of power amplifier 86.

In an open loop scheme, coupler 88 need not be used and the gain ofpower amplifier 86 may be adjusted by providing control signals to poweramplifier 86 over control path 90 without feedback from the output path.

In a closed loop scheme of the type shown in FIG. 4, feedback isobtained from the output path. With one suitable arrangement, aradio-frequency coupler such as coupler 88 is interposed between theoutput of power amplifier 86 and antenna 64. Coupler 88 may allow mostof the power from amplifier 86 to pass to antenna 64. A small fraction(typically less than a few percent) of the output power may be divertedby coupler 88 onto feedback path 92. Radio-frequency detector 94 (e.g.,a diode-based power sensor) may be used to sense the power of thediverted radio-frequency signal on path 92. Measured output power datafrom detector 94 may be provided to control circuitry 72 over path 96.Because the tap ratio of coupler 88 is known, control circuitry 72 canuse the radio-frequency output signal power measurement data on path 96to determine whether the desired output power level from power amplifier86 is being properly maintained. If adjustments are needed, controlcircuitry 72 can generate corrective control signals on path 90 in realtime. When power amplifier 86 receives these control signals, the gainof power amplifier 86 will be adjusted upwards or downwards as needed.

In configurations in which control circuitry 72 contains more than oneprocessor, each processor may share control duties while controlling thepower of transmitted radio-frequency signals. For example, controlcircuitry 72 may contain a main microprocessor for running an operatingsystem and user applications. Control circuitry 72 may also include oneor more smaller more dedicated processors such as a digital signalprocessor and microprocessor in a baseband module. In environments suchas these, each processor may run its own control process. Communicationsbetween processors may be implemented using control lines, sharedmemory, or any other suitable technique.

Illustrative steps involved in controlling transmitted radio-frequencysignal power levels in device 10 using sensor data and operational dataof the type described in connection with FIG. 3 and power controlcircuitry of the type described in connection with FIG. 4 are shown inFIG. 5. As shown in FIG. 5, device 10 may transmit and receive wirelessdata during normal operation (step 98). Transmitted wireless data mayinclude local area network data and Bluetooth® data being handled byantenna 62 in region 21 of device 10 and cellular telephone data beinghandled by antenna 64 in region 18. During operation, control circuitry72 (FIGS. 3 and 4) may use information from proximity sensor 25 andother sensors in device 10 and may use information on whichcommunications bands are being used and which communications protocolsare being used for wireless communications (e.g., from the applicationprocessor and/or baseband module) to determine whether transmit poweradjustments are warranted. Device 10 may receive transmit poweradjustment commands from network 51 (e.g., a cellular base station) thatinform device 10 that the transmit power should be adjusted up or down.Device 10 may also determine that real time power adjustments aredesirable to compensate for changes in the operating environment fordevice 10 (e.g., temperature changes). Adjustments to the power oftransmitted radio-frequency signals in device 10 in response to transmitpower adjustment commands from a cellular base station or otherconditions that are not based on the proximity of object 60 to device 10may be performed during step 100.

When control circuitry 72 determines that object (e.g., the user's head)is in the vicinity of device 10, control circuitry 72 may reduce themaximum allowable transmit power (step 102). Whenever control circuitry72 determines that object 60 (e.g., the user's head) is no longer in thevicinity of device 10, control circuitry 72 may increase the level ofthe maximum allowable transmit power (step 104). The current value ofthe maximum allowable transmit power may represent a power ceilingbeyond which the transmit power may not be raised, even if theadjustments of step 100 (e.g., response to a transmit power adjustmentcommand from a cellular base station, response to atemperature-compensation command from an internal control process indevice 10, response to a user-selected power adjustment, response tonon-proximity-sensor data such as data from an accelerometer, etc.)might otherwise require a larger power.

This is illustrated in the example of FIG. 6. In the graph of FIG. 6,transmitted radio-frequency power P from a given device 10 is plottedvertically and time is plotted horizontally. In the FIG. 6 example,device 10 is initially transmitting radio-frequency signals at a powerof P4. This power may satisfy regulatory limits on transmitted powerprovided that device 10 is not in the vicinity of the user's head. Attime t1, the user of device 10 places device 10 in the vicinity of theuser's head. The proximity between device 10 and the user's head may bedetected using one or more sensors such as proximity sensor 25. When theproximity of device 10 to the user's head is detected, the device 10lowers the maximum permitted transmit power to P3 (step 102 of FIG. 5).Even though a higher transmit power might be desired between times t1and t2 by the cellular network, the maximum allowable transmit power ofP3 is dictated by the close distance between device 10 and the user'shead (e.g., a distance of less than a few centimeters). At time t2,device 10 is removed from the vicinity of the user's head. Sensors suchas proximity sensor 25 detect this change in position, which allows theproximity-based maximum transmit power limitation to be removed (step104 of FIG. 5). Between times t2 and t3, the transmitted power fromdevice 10 is therefore maintained at power P4. At time t3, the device 10is once more placed in proximity to the user's head, so the maximumallowable transmit power is reduced to P3. At time t4, device 10 reducesits output power to P2 in response to an internally detected condition,in response to sensor data, or in response to a transmit poweradjustment command from a cellular base station. Because power P2 islower than the maximum allowable power P3, device 10 can make thisadjustment unhindered by the proximity limits imposed by the location ofdevice 10.

In making adjustments such as these, device 10 can process inputs from avariety of sensors and sources. This is illustrated in the diagram ofFIG. 7. As shown in FIG. 7, device 10 may process data from multiplesources in real time to determine an appropriate transmit power level touse in transmitting radio-frequency signals (step 112). During step 112,power output may be regulated using an arrangement of the type shown inFIG. 4 (as an example).

Data that may be used in making power level determinations includesproximity sensor data. Proximity sensor data may be received by controlcircuitry 72 from proximity sensor 25. As described in connection withtouch screen capacitance 66 of FIG. 3, touch sensor data from acapacitive touch screen or other touch screen, from a touch pad, or fromany other touch sensor may be processed by control circuitry 72 to helpdetermine whether device 10 is in proximity to object 60 (step 114).Ambient light sensor data may also be used in determining whether device10 is in proximity to object 60. For example, if an ambient light sensorsignal drops at the same time that the proximity sensor data indicatesthe presence of a nearby object, it may be concluded with greatercertainty that device 10 is in proximity to object 60. Ambient lightsensor data may be received from a sensor such as sensor 27 (FIG. 1) atstep 116.

Accelerometer data may be received by control circuitry 72 at step 118.Data from an accelerometer may be used to determine whether or notdevice 10 is in motion (and therefore likely being held by a user) or isat rest (and therefore likely not being held by a user. Accelerometerdata may also be used to determine when device 10 is being held on itsside or is being maintained in a horizontal orientation. This data maybe combined with data from a proximity sensor and other data to helpdetermine whether or not to reduce transmit power levels.

Transmit power adjustment commands may be received from externalequipment such as a cellular base station at step 108. Internallygenerated information such as information on the current communicationsbands and protocols that are being used by device 10 may be gathered atstep 110.

During step 112, control circuitry 72 may process data gathered duringany suitable combination of steps 106, 108, 110, 114, 116, and 118 todetermine an appropriate transmit power level at which to transmitradio-frequency signals from device 10.

It may be desirable to make transmit power adjustments in more than oneband. For example, during the operations of steps 110 and 112 of FIG. 7,it may be desirable to maintain the total transmitted power below aparticular level while transmission are being made in two or moredifferent communications bands. In this type of situation, increases intransmit power in a first band may be offset by automatically reducingthe transmit power in a second band.

Adjustments of this type may be made to maintain the total power levelconstant. For example, power reductions in one band may be made thatexactly offset power increases that arise in another band. If desired,power adjustments may be made unequally, by imposing weighting factorson each of the bands. In this type of scenario, an increase in transmitpower in one band may be adequately compensated by a lesser decrease intransmit power in another band when permitted by applicable regulations.Power adjustments may be made in any suitable number of bands (e.g., inone band, in two bands, in three bands, or in more than three bands).Moreover, transmit power levels in any suitable number of bands may betaken into consideration when computing desired transmit powers (e.g.,one, two, three, more than three, etc.).

FIG. 8 shows illustrative steps that may be involved in operating awireless electronic device to determine appropriate radio-frequencysignal power settings for transmitted signals in situations in which oneor more communications bands are being used. During step 98, device 10may be operated in a system. Due to automatic activity, response toexternal input, or response to a user command, the transmit powerassociated with one or more communications bands may change, asindicated by line 120. As step 100, device 10 can make suitable transmitpower adjustments in one or more communications bands to accommodate thechanges of line 120. Device 10 may then return to normal operation atstep 98, as indicated by line 122.

During step 100, adjustments may be made based on transmit power changesmade in one or more communications bands. For example, an scheduledoperation in device 10 may require that a particular communications bandbe activated or that the transmit power associated with that bandotherwise be increased (e.g., to accommodate a system power leveladjustment request, etc.). A band may also be activated or deactivatedor may be subject to other transmit power adjustments based on manualinput.

As an example, a user may desire to use a local area network (IEEE802.11) wireless communications band (e.g., at 2.4 GHz) to download afile from a local area network. At the same time, device 10 may behandling a voice call over a cellular telephone network in a GSM 2G or 3G communications band (as an example). Because the wirelesstransmissions at 2.4 GHz that have been initiated by the user in thistype of situation may contribute to the total amount of radio-frequencypower emission from device 10, it may be desirable to temporarily reducethe transmit power in the cellular telephone band to accommodate theuser's use of the 2.4 GHz band. Once use of the 2.4 GHz band is complete(e.g., because the file download is complete or because the user hasdeactivated the 2.4 GHz band), the transmit power level in the cellulartelephone band can be increased.

As another example, device 10 may automatically activate one or more GSMbands or other suitable long-range communications bands while anotherband or bands (e.g., telephone or local data) are already active. Inthis scenario, adjustments may be made to ensure that the total power insome or all communications bands remains below a desired level. Ifdesired, weighting factors may be assigned to each band to reflectpotentially different levels of importance when considering the transmitpower in those bands. These weights may be assigned based on the amountby which each band's transmitted signals are believed to be absorbed bythe user's body, based on the location of the antenna structures indevice 10 that handle each band's signals (e.g., whether radiatingtowards the user's body or away from the user's body), based onregulatory limits for each band, based on other suitable factors, orbased on combinations of these factors.

Moreover, other data may be taken into consideration when adjustingtransmit powers. For example, device 10 may use global position system(GPS) data, user-supplied location data, or other suitable data todetermine the current location of device 10. The location of device 10may then be used to determine which of multiple possiblegeographically-based regulatory regimes should be applied to theoperation of device 10. If, for example, it is determined that device 10is present in a country in which the level of allowable transmit poweris relatively large, device 10 may make adjustments during step 100 thatallow for correspondingly larger amounts of transmitted radio-frequencypower to be used by device 10. Proximity-based transmit poweradjustments and adjustments based on other factors may made in real timeto accommodate these currently applicable geographic regulatoryrestrictions.

The foregoing is merely illustrative of the principles of this inventionand various modifications can be made by those skilled in the artwithout departing from the scope and spirit of the invention.

What is claimed is:
 1. An electronic device, comprising: a capacitiveproximity sensor that detects when objects are present within a givendistance of the electronic device; a radio-frequency antenna with whichradio-frequency signals are transmitted with a transmit power; andcircuitry that adjusts the transmit power based at least partly on datafrom the capacitive proximity sensor.
 2. The electronic device definedin claim 1 wherein the circuitry comprises a power amplifier with anadjustable gain, wherein the circuitry generates a control signal forthe power amplifier that reduces the gain of the power amplifier when itis determined that an object is present within the given distance of theelectronic device.
 3. The electronic device defined in claim 1 whereinthe circuitry comprises: an adjustable gain radio-frequency poweramplifier that generates the radio-frequency signals at the transmitpower; a radio-frequency coupler that is interposed between theradio-frequency power amplifier and the antenna; and a detector thatdetects signals from the coupler to measure the transmit power.
 4. Theelectronic device defined in claim 1 wherein the circuitry comprises: anadjustable gain radio-frequency power amplifier that generates theradio-frequency signals at the transmit power; a radio-frequency couplerthat is interposed between the radio-frequency power amplifier and theantenna; and a detector that detects signals from the coupler to measurethe transmit power, wherein the circuitry generates a control signal forthe radio-frequency power amplifier that reduces the gain of theradio-frequency power amplifier when it is determined that an object ispresent within the given distance of the electronic device.
 5. Theelectronic device defined in claim 1 wherein the electronic devicecomprises a handheld electronic device having a touch sensor and whereinthe circuitry adjusts the transmit power based at least partly on datafrom the touch sensor.
 6. The electronic device defined in claim 1wherein the electronic device comprises a handheld electronic device,wherein the capacitive proximity sensor comprises a capacitive touchscreen display, and wherein the circuitry adjusts the transmit powerbased at least partly on data from the capacitive touch screen display.7. The electronic device defined in claim 1 wherein the circuitrycomprise transmitter circuitry that handles radio-frequency wirelesstransmissions in at least a first wireless communications band and asecond wireless communications band and wherein the circuitry isconfigured to make radio-frequency wireless transmit power adjustmentsin the first wireless communications band at least partly based onchanges that occur in radio-frequency wireless transmit power levels inthe second wireless communications band.
 8. The electronic devicedefined in claim 1 further comprising: at least one additional sensor,wherein the circuitry adjusts the transmit power based at least partlyon sensor data from the additional sensor concurrently with the datafrom the proximity sensor, wherein the circuitry establishes a transmitpower ceiling based on the data from the capacitive proximity sensor. 9.The electronic device defined in claim 8 wherein the circuitry preventsadjustments to the transmit power based on the sensor data that produceadjusted transmit powers exceeding the transmit power ceiling.
 10. Ahandheld electronic device operated by a user, comprising: an antennawith which radio-frequency signals are transmitted at a given transmitpower; a first sensor that generates sensor data; a second sensor,wherein the second sensor generates proximity data indicative of whetherat least part of the user is present within a given distance from thehandheld electronic device; and control circuitry that controls thetransmit power based at least partly on the sensor data and theproximity data, wherein the control circuitry establishes a transmitpower ceiling for the radio-frequency signals based on the proximitydata.
 11. The handheld electronic device defined in claim 10 wherein thesecond sensor comprises a capacitive proximity sensor.
 12. The handheldelectronic device defined in claim 10 wherein the control circuitry isconfigured to inhibit adjustments to the transmit power based on thesensor data in response to determining that the user is present withinthe given distance.
 13. The handheld electronic device defined in claim12 wherein the first sensor comprises an accelerometer.
 14. The handheldelectronic device defined in claim 13 further comprising: a proximitysensor having a light source and a photodetector, wherein the controlcircuitry controls the transmit power by processing the sensor data, theproximity data, and information from the proximity sensor in parallel.15. A method of operating a handheld electronic device, the methodcomprising: with an antenna, transmitting radio-frequency signals at atransmit power; with a capacitive proximity sensor, determining whethera user is within a given distance from the handheld electronic device;and with control circuitry, adjusting the transmit power in response todetermining that the user is within the given distance from the handheldelectronic device.
 16. The method defined in claim 15 furthercomprising: with the control circuitry, establishing a transmit powerceiling in response to determining that the user is within the givendistance from the handheld electronic device; with an additional sensor,producing sensor data; with the control circuitry, adjusting thetransmit power based on the sensor data from the additional sensor; andwith the control circuitry, preventing adjustments to the transmit powerbased on the sensor data from the additional sensor that produce anadjusted transmit power exceeding the transmit power ceiling.
 17. Themethod defined in claim 16 wherein the additional sensor comprises anaccelerometer and wherein producing the sensor data comprises: with theaccelerometer, producing accelerometer data.
 18. The method defined inclaim 16 further comprising: with the control circuitry, determiningwhether the electronic device is operating in a first communicationsmode or a second communications mode; with the control circuitry,allowing adjustments to the transmit power to exceed the transmit powerceiling in response to determining that the electronic device isoperating in the first communications mode; and with the controlcircuitry, ensuring that the transmit power is maintained below thetransmit power ceiling in response to determining that the electronicdevice is operating in the second communications mode.
 19. The methoddefined in claim 18 wherein the first communications mode comprises a 2Gcellular communications mode and wherein the second communications modecomprises a 3G cellular communications mode.
 20. The method defined inclaim 18 further comprising: wherein the electronic device wirelesslycommunicates using time division multiplexing in the firstcommunications mode and wherein the electronic device does notwirelessly communicate using time division multiplexing in the secondcommunications mode.